Aircraft ski



Dec. 5, 1950 I F. J. DITTER 2,532,610

AIRCRAFT SKI Filed July 9, 1948, s Sheets-Sheet 1 INVENTOR FRANCIS J.DITTER ATTORNE F. J. DITTER Dec. 5, 1950 AIRCRAFT SKI 3 Sheets-Sheet 2Filed July 9, 1948 DITTER ATTORNEY I INVENTOR FRANCIS AIRCRAFT SKI Dec5,

3 Sheet t 3 Filed uly 9, 1948 l vENTo Y m m D Mug 8. C a N A R F Y B N.9 C! Patented Dec. 5, 1950 UNITED STATES PATENT OFFICE AIRCRAFT SKIFrancis J. Ditter, Minneapolis, Minn.

Application July 9, 1948, Serial No. 37,895

13 Claims.

The present invention relates to an aircraft ski and more particularlyto an aircraft ski which is retractable relative to the wheel shaft ofthe conventional landing gear of the airplane.

Heretofore, aircraft skis have been mounted on the wheel shaft of theairplane and for this purpose it has been customary to remove the wheelof the landing gear and to replace the wheel with a ski which wasmounted upon the wheel shaft. This procedure has not been undulycumbersome in the case of small aircraft which are relatively easy tolift such that the landing wheel may be removed and the ski substitutedWithout undue difiiculty. This, however, has been somewhat inconvenient.In the case of heavier and more complicated aircraft landing gear,however, the change from wheel landing gear to skis has been much morecumbersome. Convenient apparatus for supporting a heavy aircraft for thepurpose of changing from wheels to skis may not be available in variousoutlying airports. Moreover, the structure of such landing gears isusually quite complicated, and it would involve a considerable amount ofwork to remove a landing wheel and to substitute an aircraft ski.

Furthermore, aircraft equipped with only a single type of landing deviceis limited to operation under conditions for which such landing deviceis adapted. Thus a plane equipped with wheels only is limited to takeoffand landing on surfaces permitting the use of wheels. Likewise, a planeequipped solely with skis is limited to operation on snow or ice coveredfields. A further limitation arises for example when it is desired tomove a plane from a hangar to a snow covered field for take off. Underthe usual circumstances it is necessary to have wheels in place for thepurpose of moving the plane to the snow covered field, at which pointthe wheels may be removed and skis applied.

It has been found desirable, therefore, to devise a mechanism wherebythe aircraft wheel may be allowed to remain on the wheel shaft of theconventional landing gear and to provide an auxiliary shaft on which theski may be mounted, such shaft being movable relative to the wheel shaftso that both ski and wheel may be mounted on the aircraft at the sametime, and such that it is possible to move one landing device from aninoperative position into an operative position without the necessity ofremoving the other landing device. This movement of the auxiliary shaftrelative to the wheel shaft may be effected mechanically by suitablemeans controllable by the pilot from the cockpit, or may be effected byvarious means operative from a position on the ground as will bedescribed more fully hereinafter.

By this means it is possible to readily shift the skis from aninoperative to an operative position and vice versa. Thus it is possibleto have the wheels in position for moving the plane from the hangar tothe field at which point the switch from wheels to skis may be readilyaccomplished. In those instances in which the relative movement of theskis is controllable from the cockpit it will be apparent that theswitch from wheels to skis or vice versa may actually be effected duringflight such that it is possible to take off on one type of landingdevice and to land on the other type. It

is also possible as will be seen hereinafter to adjust the relativeposition of the ski and to lock it in that position so that takeolfs andlandings may be effected on any type of surface whether dry or coveredwith snow or ice. This is accomplished by having the wheel protrudebelow the ski sufficiently that the wheel will bear the load Without theski contacting the landing surface when landing is effected on a drysurface or on one on which the snow or ice is solidly packed. Onsurfaces covered with loose snow the protruding wheel will pack the snowsufficiently that the ski contacts the snow and actually bears most ofthe load.

It has also been found desirable to provide an aircraft landing ski of adivided nature such that a part of the ski is on each side of thelanding wheel. This is particularly useful in the case of large aircraftin which the necessary area of a ski is large, and where it is desirableto apply the load to the ski as close as possible to existing shockabsorbing devices.

It is, therefore, an object of the present invention to provide a novelaircraft ski so constructed that it can be mounted on the landing gearof the aircraft while the landing wheels are in position, such that theski may be moved into and out of operative position without affectingthe position of the landing wheel.

It is a further object of the present invention to provide such anaircraft ski in which the ski is movable from an operative intoaninoperative position and vice versa by means of controls from a remotepoint.

It is a further object of the invention to provide such an aircraft skiin which the ski is movable from operative to inoperative position andvice versa by manual means on the ground.

It is a still further object of the present invention to provide a novelski of divided structure which surrounds an aircraft wheel, such thatthe ski and the wheel may be in position on the aircraft landing gearsimultaneously, and that the weight is distributed directly beneath theconventional shock absorbing equipment.

The invention will be more fully apparent from the following descriptionof the invention with particular reference to the drawings in whichFigure l is a perspective illustrating a preferred embodiment of theinvention, showing the divided ski structure and the application to thisstructure of the mechanism for moving the ski into and out of operativeposition while the wheel is in position on the wheel shaft;

Fig. 2 is a plan view of the ski illustrated in Figure 1;

Fig. 3 is a fragmentary cross-section of the hub showing a means formounting the ski on the wheel shaft;

Fig. l is a fragmentary perspective of the hub shown in Fig. 3 and is anenlarged fragmentary View of the hub shown in Figure l;

igs; 5 and 6 are side elevations partly in section illustrating theposition of the ski relative to the wheel in the two limit positions ofmovement of -the'ski relative to the wheel;

Fig; 7 a fragmentary side elevation partly in section illustrating amodifi ation of the inven tion and of means for locking the ski in itstwo limit positions;

Fig. 8 is a cross-section of the locking mechanism of '7 illustratingthe locking mecha nism in an intermediate position; and

Fig.- 9 is a fragmentary elevation of a further embodiment of theinvention illustrating a simplified version thereof.

lifitii reierence to Figures 1 and 2, the ski is composed of twosections A and B, which'are of a generally similar nature. The ski isgenerally constructedin accordance with the disclosure of my copendingapplication Serial No. 706,883, filed October 31, 19%, entitledAircraftSki. In ac cordance with the teachings of that application,theski is composed of a base shoe 2i, vhich preferably is of relativelyheavy gauge sheet metal, preferably aluminum or magnesium, althoughothermaterials such as plywood may be used. This base shoe has a contour of agenerally U-shaped nature as shown in the plan view of Fig. 2; The frontend of the'ski 22 is in the position of the base of the U and isupturned somewhat for the purpose of climbing on top of snow andgradually packing it down. This toe of the ski extends backward a shortdistance and then the-sheet is cut out as indicated by space which isforward of the normal position of the wheel. .he base of the ski ispreferably cut out furt er at it to provide maximum clearance for thewheel. The cut-out space 23 forward of the wheel serves the iollcwingpurpose. As the ski travels along snow-covered ground, it is found thata considerable quantity of snow'blows over the top of the front end ofth ski and would nor mally tend to pile up in the space 23 were the baseof the shoe continuous across this space. It is foundthat by having thisspace cutout, the snow may fly over the toe of the ski and down intospace and is then packed by the oncoming wheel. In this way it is foundthat relatively little snow piles up on. the ski and thus excess weightduring flight is avoided.

Superimposed on the base shoe are a pair of. inverted channel members25, which preferably have an inverted t cross-section with side flangesfifi extending outwardly from the ends of the V. The inverted V-shapedchannels are preferably base and shoe which curves upwardly both at thetoe heel. The base shoe may be curved substany continuouslylongitudinally, but the curvais more pronounced at thetoe and heel.larger skis'the intermediate section of the skis length may besubstantially fiat, whereas in smaller skis it may be desirable to havethe base shoe in a more or less continuous curve.

ihe inverted channel members may be attached to the base shoe in anysuitable manner as by rivets passing through flanges 25 and through thebase shoe, by spot-welding, bolting, or in any other suitable manner.The various structural elements of the ski may be attached to thesechannels through saddle members 29, 33, andili, respectively; The saddlemembers 28 correspond to the shape of the channel member at this pointand are principally for the purpose of; reinforcing the channel at thispoint and for distributing load over a wider section of the channel.Afront tie member 33 extends from one side of the ski to the other andis attached to the saddle members 29. The saddle members 2% may beefsteel and the tie member 33 may likewise be of steel and attached to thesaddle by means of weids It is apparent, however, that the material ofconstruction of members 29 and may be varied and if desired these mayalso be constructed of light metals such as aluminum or mag nesiinn, andother means of fastening may be em- A reinforcing member 34 may beattached to-the base shoe and the tie member 33 to strengthen thestructure at this point.

Saddle'rnembers (ii are provided with lateral tubularsecticns 3% whichextend inwardly between the two sections A and B of the ski. Sections 36terminate inwardly in flanges to which may be attached flanges ontubular section 38. These flanges are preferably bolted together suchthat they may be readily removed for a purpose to be describedhereinafter.

The ski may be rigged for its position in flight and during taxiingoperations in any suitable manner. In Figures 1 and 2, I haveillustrated the use of an airfoil 60 for this purpose. This airfoil issupported by a pair of brackets 6i extending upwardly from the heel endof the sections A and B. This is in accordance with the teachings of mycopending application Serial No. 779:,173, filed October 10, 1947,entitled Rigging for Aircraft Ski. The airfoil is preferably supportedon the brackets M by bolts 42 (Figs. 5 and 6), in order that the airfoilmay be readil removed for a purpose to be described later.

The ski isattached. to the aircraft landing wheel shaft as follows. Thesaddles are vided wi h upstanding flanges which "n turn are suitablybraced laterally b members ib. channels 25 are cut away in the areaenclosed by the pair of flanges and the end flanges A lever arm 38extends down between the pair of flanges-5 5 and is suitably pivotedtherebetween by means of pivot The lever arm in tion A extends down intothe channel member 25 the lower end of the arm is connected to ahydraulic cylinder generally indicated at 5 3 Figs.-5 and 6. Thishydraulic cylinder is connected to a hydraulic system through leads 5iand 52-.which may extend to controls in the cockpit. In the skiillustrated in Figure l, the lever arm 48 in section B need notnecessarily be connected with a hydraulic cylinder for the followingreason. The two lever arms 48 are connected by means of a shaft 55 whichextends through the hollow wheel shaft of the aircraft and in thismanner levers 48 may both be operated by a single hydraulic cylinder.The details of this structure are shown in Figs. 3 and 4. This shows theapplication of this ski to the conventional -47 landing gear. The wheelshaft of this landing gear is illustrated as a hollow shaft 66. At eachend of this shaft there is provided a sleeve 5| having an upstandingflange 62 for attachment to the brakes. The sleeve 6| extends somewhatbeyond the end of wheel shaft 56. Conventionally sleeve 6| is attachedto wheel shaft 60 by means of a pin which passes directly through thesleeve and through the wheel shaft, and inasmuch as the presentarrangement provides for passing shaft 55 through the center of wheelshaft 6%, this straight pin has been replaced by a pair of pins 63 whichextend only through sleeve El and wheel shaft 50, thus leaving theentire area of the center of wheel shaft 60 for shaft 55. Pins 6| may befastened to a split collar 64, the two halves of which are clampedtogether by means of suitable ears, thereby holding pins 63 in place.Sleeve member Si is supported from the aircraft by means of supports 65which in turn are connected to the shock gear of the airplane. Supports65 terminate in a split hub section 55 which surrounds the sleeve BI andwhich is keyed thereto by means of key 61. Hub section it may beprovided with inwardl extending protrusions 63 which fit intocorresponding grooves in the circumference of the sleeve 6| to preventlateral displacement of the hub member. In this manner the wheel'shaft5B is held against rotation relative to brake flange 52 and relative tothe supports 65.

Shaft 55 is illustrated as a hollow shaft extending through the hollowwheel shaft 60. For added shear strength at the outward end of shaft 55,it may be provided with a solid stub shaft E53, which extends inwardlyfor a suitable distance to carry the shear load. Shaft 55 is supportedin the wheel shaft E593 by means of a bronze bushing H which may bepressed into the end of sleeve 6! beyond the termination of shaft 65.Lever 48 is provided with a split cap 52 which surrounds shaft 55. Thissplit cap portion has a section i3 which extends over and partiallysurrounds the end of sleeve 5! but is spaced therefrom. The two halvesof the split cap 12 are held in position by a retaining ring 14 whichsupports the two halves on the internal end and by a retaining ring 15which surrounds a cut-down portion of the outward end of the split capI2. Lever arm 48 is held from rotation relative to shaft 55 by means ofbolt '56 which extends through the retaining ring 15 through the splitcap 12 and through the shaft 55 and the stub shaft "it. Retaining ring14' may be held in position by a series of set screws 11. For assemblypurposes retaining ring it ma be moved laterally adja cent the end ofhub 56. Bolt 15 may be removed and retaining ring 15 slid off to make itpossible to separate split cap 12, and thus permit removal of shaft 55.

Figs. 5 and 6 illustrate cut-away side elevations of the ski of Figure 1showing the ski in the two limit positions. In Fig. 5 the ski isretracted and the wheel extends through for contact with the landingsurface. In Fig. 6 the ski is lowered and is in operative position forlanding. A small segment of the wheel may extend below the ski surfacein Fig. 6, but this readily compresses upon landing and the essentialload is carried by the ski. This serves several purposes. Thecompression of the tire absorbs some of the shock of landing, forexample on ice. Furthermore the protrusion of the wheel makes the brakespartially operable both for stopping and turning. The lower end of thehydraulic cylinder is pivotally attached to the base of the ski and isnot movable longitudinally relative to the ski. Hydraulic lines 5! and52 connect to the hydraulic system of the plane and to suitable controlslocated in the pilots cockpit. It will be apparent that the introductionof hydraulic fluid into line 5| moves the piston from the position shownin Fig. 6 to the position shown in Fig. 5. Introduction of hydraulicfluid into line 52 and the venting of line 5! will result in theretraction of the piston from the position shown in Fig. 5 to theposition shown in Fig. 6. It should be pointed out that in Fig. 5 theweight of the ski is supported by means of the fluid in the hydrauliccylinder. This is not an undue burden on the hydraulic system in view ofthe fact that the total weight of the ski may not be particularly great.In Fig. 6 the lever arm 18 meets stop as when the hydraulic cylinder isin the fully retracted position. It will be apparent, therefore, thatsince the thrust of the motor applies a forward thrust to shaft 55 andthe drag of the ski provides a rearward thrust on the ski, that the loadof the forward thrust will be taken by the lever arm 48 in contact withstop 89, and no thrust will be taken by the hydraulic system. It isevident, therefore, that this arrangement provides for a minimum loadapplied to the hydraulic system.

For purposes of mounting the ski on an aircraft, this may beaccomplished very simply by removing the rigging airfoil 4b and byremoving removable cross member 38. Shaft 55 and the structureassociated therewith for mounting on the wheel shaft 65 may likewise beremoved. The ski may then be moved backward into position about thewheel which is in position on its wheel shaft. Shaft 55 may then be slidthrough the center of wheel shaft 60. Retaining ring Hi may be slid ontothe end of sleeve 6 l. The outside end of shaft 55 may then be placed inposition on the split cap section of lever 58, after which the remainingportion of the cap may be applied. Retaining ring 14, may then be movedinto position and secured by screws 11 and likewise retaining ring 15may be placed over the outer end of the cut-down section of the splitcap. Bolts '55 may then be placed through the entire assembly.Thereafter tie tube 35 may be bolted into position, as likewise may bethe rigging airfoil 40, and the ski is in condition for operation. Itwill be apparent that saddles 33 may be provided with suitable accessholes for the purpose of enabling one to get at the hydraulic cylinderfor adjustment or maintenance.

For application of this type of ski to the wheel shaft of an aircraftlanding gear in which the wheel shaft is solid or is too small so thatit is not possible to pass the shaft 55 through the center of the wheelshaft, it is possible to provide a pair of hydraulic or pneumaticcylinders, in which event lever arms 48 would be identical. Thesecylinders may be connected to a divider which supplies identicalquantities of fluid to each cylinder, in which case the levers wouldoperate in unison and would be properly synchronized.

It is also possible to operate the levers 48 by means of a commonelectric motor which may be positioned in either section of the ski orin the cross-tube 33 or in a housing adjacent the cross tube. Thissingle motor may be directly geared to each of the lever arms 48 andthus operate them in unison.

With reference to Fig. 7, this illustrates a further embodiment of theinvention in which means are supplied for locking the lever arm in itstwo limit positions. This figure shows the inverted channel member 25,the base shoe 2 I, and a modifled'saddle member IQI, which conforms tothe contour of the channel member 25 but has an opening therein alongthe ridge of the channel. Near the opening, the saddle I9! is reinforcedby means of auxiliary saddle I32. A pair of saddle flange members I83are inserted in the opening in the saddle IBI and suitably supportedtherein, as for example by means of welding It l. These two saddleflanges are spaced apart and are further supported in this spaced-apartposition by means of side plates I535 and I55 which are suitablyattached to the saddle flange members, as for example by means ofwelding. Lever arm I H3 is pivoted about a pin Iii which passes throughthe lever arm and which in turn is supported in the saddle flanges IE3.posed of an up-standing section II 2 which is pivoted at its upper endin the wheel shaft I I3 of the aircraft landing gear. The lever arm isprovided with a lower section H5 which is ofiset somewhat from the uppersection IIZZ. This section of the lever arm is provided at its lower endwith an elongated slot H8. As shown in Fig. 8, the lower section of thelever arm is bifurcated adjacent the elongated slot I It. The lowersegment of the lever arm 1H3 is connected to the piston rod I I8 ofhydraulic cylinder I I t by means of pin I29. The lefthand end of thehydraulic cylinder H9 is pivoted to permit it to move in accordance withthe dictates of the lever arm I I5. The cut-down end I2I of thehydraulic piston rod is disposed between the two segments of the forkedend of lever I It and the pin I28 passes through the respective members.In the intermediate position of movement of the lever arm Hi), the pinI28 rides on the upper edge I22 of guide members I23 which are arcuatein outline as shown in Fig. 7. Pin [2% is maintained in position bymeans of side plates I25 which are sup ported dependently from thesaddle flanges I83 by means of rivets or bolts or welds I25. The guidemembers E23 are suitably supported by side plates I 2d.

The righthand end of the arcuate guide I23 is substantially parallel tothe center line of the lower section I I5 of lever arm I It. Thelefthand end of arcuate guide I23 is likewise parallel to the centerline of this lower section of the lever arm in the other limit position.In this manner any load applied to the pin I23 through the lever arm II?will be normal to the end surface of the arcuate guide, and it will beapparent, therefore, that the lever arm will thus be locked in thisposition. It will also be apparent that piston rod I I8 has a componentof force in a direction along the center line of the lower section We ofthe lever arm toward the pivot III when the lever arm is in either ofits two limit positions, and when force is applied to the piston rod toeffect movement of the lever arm toward its other limit position. Thiscomponent of force in the direc- The lever arm is comtion of pivot I I lis sufficient to raise the pin I25- in the slot H5 until it will ridealong the top I22 of the arcuate guides I23. This position of the pin isillustrated in Fig. 8.

With further reference to Figs. 7 and 8, it will be apparent that theposition of lever arm I I 5 in Fig. 7 is the position in which the skisare in operative position. The forward end of the ski is to the left inFig. 7. The thrust of the motor on Wheel shaft IE3 is to the left, andaccordingly this thrust is limited by means of stop I39 on side plateI24 when this stop comes in contact with the adjacent point ESI on thelower section I I 5 of the lever arm. In this manner there is no thruston the hydraulic system or on the rod I I8 to resist the thrust of themotor and the drag of the ski. The conditions on landing are the same asduring take-01f.

In the reverse position of the lever arm III], that is, in which thelever arm is moved so that its lower end is in the limit position on theleft in Fig. 7, the weight of the ski on the lever arm will be borne bythe end of the arcuate guide I 23 through the pin I2ii and will not haveto be borne by the hydraulic system. A stop I32 is provided adjacent theleft hand limit position of the lever arm. When the lever arm hits thisstop, further movement of the piston serves to move pin I26 into lookingposition at left end of arcuate guide. It is apparent, therefore, thatby this means there has been provided a locking device for locking theski in its two limit positions and for taking the thrust of the motor,the drag and the weight of the ski on the actual structural devices ofthe ski without applying any load on the actuating mechanism forchanging the position of the ski. This locking device is of considerableimportance in insuring that the ski will remain in whichever position itis during a takeoff or landing operation and to prevent any change inthe position of this ski at a time when change might be disastrous.

In Fig. 9 I have illustrated a further embodiment of the invention withmeans for locking the ski in any of the plurality of positions. The skihas the usual channel section 25 and base shoe 2I. It may be providedwith any suitable saddle I35 which again conforms to the contour of thechannel 25. The saddle I35 may be cut out at or adjacent the base of thechannel 25, and a pair of flange plates I 36 suitably supported in theresultant opening. These flange plates may also be supported outside thechannel where desired. A lever arm I37 having an arcuate segment I 38 ispivoted at I 39 to the flange plates I36. The lever arm I3? is providedwith a hole for attachment to wheel shaft I of the aircraft landinggear. A locking hole having pin I ll therein is provided in the rearwardend of the flange plates I36. A series of locking holes I42 are providedin lever arm I37 along the arc of a circle having a radius from pivotI39 to locking pin I lI. It will be apparent that the lever arm may beadjusted to any desired position and locked in this position by means ofpin MI passing through the flange plates I35, through holes I t2, andthrough the flange plate on the other side.

The lever arm I37 has been illustrated as having a lower section I 33having hole I M therein for attachment to a suitable actuating devicesuch as a hydraulic cylinder, if such actuating device is desired.

The adjustability of this structure is useful in the followinginstances. Under some circumstances landings and take-offs may beperformed for a long period of time under constant conditions of eitherice or snow or at other times under constant conditions of freedom fromice and snow. Under these circumstances, it may be desirable to adjustthe ski to the position necessary for the operating conditions and toleave it in this position. On other occasions, however, it may be foundthat one may be taking off from an airport having ice or snow thereonand may be traveling to another airport which is free from thiscondition. Under these circumstances, it may be desirable to adjust therelative position of the ski such that the landing wheel protrudes belowthe surface of the ski a sufficient distance that it will take the loadof the plane on landing on non-icy conditions. In this way it ispossible to either take off or land on a dry airport. By carefullyadjusting the ski, it is possible to have the ski take the load in theevent that landing or take-off is attempted on an airport where anydepth of snow is encountered. Under these circumstances, the fact thatthe wheel may protrude below the lower surface of the skiis notparticularly disadvantageous inasmuch as the ski tends to take the majorportion of the load and the tire will compress and thus permit the skito take the larger portion of the load.

While various modifications of the invention have been described, it isto be understood that the invention is not limited thereto and thatother modifications may be made without departing from the spiritthereof. while illustrations in the drawings have been with particularreference to the divided ski arrangement, it is evident that thearrangement for the raising and lowering of the ski relative to thewheel shaft may be applied equally to single skis which are mounted oneither side of a wheel. It is likewise apparent that while hydrauliccylinders and H9 have been described, these may be pneumatic cylinders,or electrical or other screw jack devices.

I claim as my invention:

1. An aircraft ski having a pedestal intermediate the ends thereof, alever arm pivoted on said pedestal and extending upwardly therefrom,means on the upper end of said lever arm for pivotally mounting saidlever on the wheel shaft of an airplane said lever arm also extendingdownwardly from said .pivotal connection on said pedestal and means onthe ski for moving said lever arm about said pivo-t.

2. An aircraft ski comprising a base shoe, an inverted channel membersupported thereon, a pedestal on said channel member, a lever armpivoted intermediate its length on said pedestal, and means on one endof said lever arm for pivotally attaching it to the wheel shaft of anairplane.

3. An aircraft ski comprising a base shoe, an inverted channel membersupported thereon, a pedestal supported on said inverted channel, alever arm pivotally supported on said pedestal and extending through thebase of said channel member into the internal portion of the ski, meansat one end of said lever arm for attaching said arm to the wheel shaftof the landing gear of an airplane, and means on the end of said leverarm in the interior of said ski for rotating said lever arm about saidpivot.

4. An aircraft ski comprising a base shoe, an inverted channel membersupported thereon, a pedestal supported on the channel member, a

For example,

lever arm pivoted intermediate its length on said pedestal, the lowerend of said lever arm extending through the channel member into theinterior of the ski, a hydraulic cylinder having one end pivotallyattached to the ski, the other end pivotally attached tothe lower end ofthe lever arm, the remaining end of said lever arm having means thereonfor attachment to the wheel shaft of an airplane.

5. An aircraft ski comprising a pair of inverted channel membersextending generally parallel, a base shoe of generally U-shaped form,the arms of the U extending beneath the inverted channel members andbeing attached thereto, the base of the U extending between the channelmembers at the forward end of said channel members, a removable supportmember extending from one channel member to the other near the rearwardends of said channel members, and means on said channel members forsupporting an aircraft Wheel therebetween.

6. An aircraft ski having a lever arm pivoted thereon, said lever armbeing pivoted intermediate its length, means at one end of said leverarm for attachment to: the wheel shaft of an airplane, means at theother end for movement of said lever arm about said pivot between twopredetermined limits, and locking means for locking the lever arm ateither of said limits.

7. An aircraft ski having a mounting pedestal intermediate its length, alever arm pivotally mounted on said pedestal intermediate the length ofthe lever arm, means at one end of said lever arm for attachment to thewheel shaft of an airplane, means for rotating said lever arm about saidpedestal pivot, and an abutment on said pedestal adapted to contact saidlever arm to limit its movement in one direction.

8. An aircraft ski having a mounting pedestal thereon, a lever armpivotally mounted on said pedestal, means on said lever for attachmentthereof to the Wheel shaft of an airplane, said lever arm having anarcuate segment, a plurality of locking elements along the edge of saidarcuate segment and locking means supported on said pedestal and adaptedto cooperate with said locking elements, whereby said lever may belocked in any of a plurality of positions.

9. An aircraft ski comprising a pair of inverted channel membersextending generally parallel, a U-shaped base member having the arms ofthe U extending beneath the inverted channel members and attachedthereto, the base of the U extending between the channel members at theforward end thereof, each of said inverted channel members having apedestal mounted intermediate the length thereof, a pair of lever arms,one mounted in each of said pedestals, one end of one of said lever armsextending through the channel member into the interior of the ski, ashaft rigidly connected tothe out-' wardly extending ends of the leverarms, and means within said channel section for actuating said one ofsaid lever arms and rotating it relative to said pivot.

10. An aircraft ski comprising a base shoe, an inverted channel membersupported on said base shoe, an opening in said channel member at thebase thereof, support means mounted in said opening and extendingupwardly from the base of the channel, a lever arm supportedintermediate its length on said support member, a portion of said leverarm extending upwardly from said pivot and having at its uppermost end76 means for attachment to the wheel shaft of an airplane, the lowerportionxof the lever arm extending through theopening in the channelintothe interior of the ski and being pivotally connected at its lower endto an-actuatingmeans, said-pivotal connection including a pin passingthrough the actuating means and through an elongated slot in thelowerend of the lever arm, said elongated slot extending generally alongthe center line of the lower section of the lever arm, arcuate guidemeans for said pivot pin, said arcuate guide means having a radius lessthan the distance from the intermediate pivot of the lever arm to theoutward end of the elongated slot, the ends of the arcuate guide beingsubstantially parallel with the center line of the lower portion of thelever arm at its corresponding limit of movement.

11. An aircraft ski according to claim 10 in which the lower end of thelever arm is bifurcated and the end of the actuating means is disposedbetween the bifurcations of the lever arm and the pivot pin extendsthrough the entire assembly, and in. which the pin is free for rollingmovement relative to the actuatingmeans, the bifurcated lever arm, andthe arcuate guide, the pin being held against lateral displacement byplates disposed adjacent the arcuate guide.

12 12'. -An' aircraft ski assembly: comprisinga hollow wheel-shaft; aninner shaft passing through said hollowwheel shaft, a pair of skisections extending generally parallel, a pair of lever arms, one of-saidlever arms being pivotally supported oneach of said ski sections, oneend of each of said-lever arms being attached to said inner shaft. 13.'An aircraft ski'acco-rding toclaim 12in whichone of said leverarmsextendsbelow said pivot andhas attached to the lower end thereofmeans for moving-said lever arm about said pivot.

FRANCIS J. BITTER.-

REFERENCES CITED The following references are -of record inthe file: ofthis patent:

UNITED STATES PATENTS Number H Name- Date" 1,844,295; Perry Feb. 9,;19322,340,080" Ringnel Jan.'25,' 1944 FOREIGN 1 PATENTS- N tric-fiberCountry Date 71,226 Sweden Feb. 24, 1931

